Sulfur Hexaflouride

What gas is colorless, odorless, non-toxic, non-flammable, and if you fill a balloon with it, it'll drop like a rock? Since the title of this post is Sulfur Hexaflouride you probably got the answer right.

This stuff is like anti-helium. Even in that if you breath it in and talk, your voice gets substantially lower! But the most amazing thing you can do with Sulfur Hexaflouride is float stuff in it. Check this video!

Top Men want a tank of this stuff to play with.

UPDATE (1/16): Here is a "lower your voice" movie.

(Thanks Tinselman)